This invention relates to a method and apparatus for production of geothermal fluid from the liquid dominated geothermal reservoir and a method and apparatus for generating electric power by utilizing the geothermal fluid.
Geothermal energy is becoming important as a substitute for fossil fuel. According to a present method of producing geothermal fluid, the produced hot fluid is separated into steam and hot water for utilizing the steam for electric power generation.
With this method, however, as the geothermal fluid rises through the production well and approach the ground surface, a portion of the hot water evaporates due to pressure drop and the fluid temperature is lowered by evaporation.
The drop of temperature and pressure of the fluid in the well causes not only decrease of available energy of the geothermal fluid but clogging of the well due to precipitation of solute from the fluid and thereby shortening the life of the well casing.
Various methods have been proposed to prevent evaporation of the hot water as well as the temperature drop thereof. For a exmple, an electrically driven water pump is installed in a well to pump up the fluid. However, installation of a water pump in a deep well is difficult or impossible under a certain condition.
Moreover, according to the prior art turbine electric power generating plant utilizing geothermal fluid, the produced hot water is flashed to generate steam which is supplied to a steam turbine coupled to a generator together with steam generated from the production well. Consequently, the temperature of the steam supplied to the steam turbine is lower than that in the reservoir, thus failing to efficiently use the geothermal energy.
To obviate this difficulty it has been proposed to directly supply produced geothermal fluid to a total flow turbine without flashing hot water to drive the turbine with a mixture of steam and hot water. However, temperature drop of the geothermal fluid in the production well is inevitable.